This invention is directed to an electronic timepiece having a main oscillator circuit including a first time standard and a second oscillator circuit including a second time standard, the respective time standards of said main and secondary oscillator circuits having different temperature characteristics, and, in particular, to an electronic timepiece for measuring a phase difference in the high frequency time standard signals produced by respective first and second oscillator circuits as a result of temperature being varied by more than 10.degree. from the specific temperature at which the time standard of the main oscillator circuit admits of its inflection peak to thereby utilize the phase difference to adjust the frequency rate of the timekeeping circuitry.
A problem that inures to electronic timepieces utilizing piezoelectric vibrators as a time standard is the variation in the frequency rate of the vibrator caused by the temperature characteristics thereof. Although attempts have been made to utilize capacitors, having a temperature characteristic similar to that of the piezoelectric vibrator in the oscillator circuitry, at best, such temperature compensating capacitors can only approximate the temperature characteristics of the quartz crystal vibrator and, hence, cannot completely compensate therefor. Although piezoelectric vibrators, capable of operating at very high frequencies with little response to changes in temperature, have been provided, the high frequency of vibration (mega-Hertz range) has been found to be less than completely satisfactory in electronic timepieces. Specifically, piezoelectric vibrators, capable of operating in the mega-Hertz range are extremely large, thereby rendering it difficult to miniaturize the electronic timepiece. Secondly, by providing a time standard in the mega-Hertz range, the timekeeping circuitry is required to operate at higher switching speeds, thereby consuming an excess of power, and, hence, shortening the life of the battery utilized to power the electronic wristwatch. Accordingly, a small-sized electronic wristwatch that utilizes the temperature characteristics of first and second piezoelectric vibrator time standards to reduce variations in the timing rate caused by changes in temperature is desired.